Meng Yonghong, Dong Guiru, Zhang Chen, Ren Yuanyuan, Qu Yuling, Chen Weifeng
College of Food Engineering and Nutritional Science, Shaanxi Normal University, 620 West Chang'an Avenue, Chang'an, 710119, Xi'an, People's Republic of China.
Institute of Enzyme Engineering, Shannxi Academy of Sciences, No.16 East Renmin Road, Lintong District, Xi'an, 710600, People's Republic of China.
Biotechnol Lett. 2016 Apr;38(4):673-9. doi: 10.1007/s10529-015-2023-x. Epub 2015 Dec 28.
To study the effect of Ca(2+) on glutamate dehydrogenase (GDH) and its role in poly-γ-glutamic acid (γ-PGA) synthesis in Bacillus natto HSF 1410.
When the concentration of Ca(2+) varied from 0 to 0.1 g/l in the growth medium of B. natto HSF 1410, γ-PGA production increased from 6.8 to 9.7 g/l, while GDH specific activity and NH4Cl consumption improved from 183 to 295 U/mg and from 0.65 to 0.77 g/l, respectively. GDH with α-ketoglutarate as substrate primarily used NADPH as coenzyme with a K m of 0.08 mM. GDH was responsible for the synthesis of endogenous glutamate. The specific activity of GDH remained essentially unchanged in the presence of CaCl2 (0.05-0.2 g/l) in vitro. However, the specific activity of GDH and its expression was significantly increased by CaCl2 in vivo. Therefore, the regulation of GDH and PGA synthesis by Ca(2+) is an intracellular process.
Calcium regulation may be an effective approach for producing γ-PGA on an industrial scale.
研究Ca(2+)对纳豆芽孢杆菌HSF 1410中谷氨酸脱氢酶（GDH）的影响及其在聚γ-谷氨酸（γ-PGA）合成中的作用。
在纳豆芽孢杆菌HSF 1410的生长培养基中，当Ca(2+)浓度从0变化至0.1 g/l时，γ-PGA产量从6.8 g/l增加至9.7 g/l，而GDH比活性和氯化铵消耗量分别从183 U/mg提高至295 U/mg以及从0.65 g/l提高至0.77 g/l。以α-酮戊二酸为底物的GDH主要以NADPH为辅酶，其Km为0.08 mM。GDH负责内源性谷氨酸的合成。在体外，当存在CaCl2（0.05 - 0.2 g/l）时，GDH的比活性基本保持不变。然而，在体内，CaCl2显著提高了GDH的比活性及其表达。因此，Ca(2+)对GDH和PGA合成的调节是一个细胞内过程。
钙调节可能是工业规模生产γ-PGA的有效途径。
